Morphologic alterations in HeLa cells deprived of serum and amino acids were studied by light and electron microscopy. After complete deprivation for 1, 3, or 6 hours, many cells contained autophagic vacuoles enclosing clearly recognizable cell organelles. The proportion of cells showing autophagy rose from 4 to 37% in the first 3 hours of deprivation. Acid phosphatase reaction product was localized within many of the autophagic vacuoles by a modified Gomori method. After 12 to 24 hours of deprivation, many membranous residual bodies were noted within the starved HeLa cells. These electron microscopic studies indicate that complete deprivation of serum and amino acids provides a useful model for the further study of cellular autophagocytosis.